大样本恒星演化研究组知识库

Recent observations discovered several long-orbital-period subdwarf B (sdB) stars with main-sequence companions. Their orbital periods are far beyond that expected from stable Roche Lobe overflow (RLOF), and then challenge this scenario to form these systems. In this contribution, we show a unique sdB mass – orbital period relation for sdB binaries produced in this way, given the progenitors of the sdB stars have initial masses below the helium flash mass. The observed orbital-period distribution of long-period sdB binaries can be well explained based on this relation. The mass – orbital period relation can be tested observationally if the mass of the sdB star can be determined precisely, e.g. from asteroseismology. Finally, we revised the orbital period distribution of sdB binaries produced by the first stable RLOF channel for the best fitting model of Han et al. (2003), showing a peak around 830 d.